Zoom lens system, interchangeable lens apparatus and camera system

ABSTRACT

A zoom lens system comprising a negative first lens unit, a positive second lens unit, a negative third lens unit, and a positive fourth lens unit, wherein the second lens unit is composed of an object-side second lens unit and an image-side second lens unit, the object-side second lens unit has positive optical power, an aperture diaphragm is located between the object-side second lens unit and the image-side second lens unit, and the conditions: −0.5&lt;f 2O /f 2I &lt;1.0 and 0.12&lt;d 2O /f W &lt;0.35 (f 2O : a composite focal length of the object-side second lens unit, f 2I : a composite focal length of the image-side second lens unit, d 2O : an optical axial distance from a most object side lens surface of the object-side second lens unit to the aperture diaphragm, f W : a focal length of the entire system at a wide-angle limit) are satisfied.

RELATED APPLICATIONS

This application is a Continuation of International Application No.PCT/JP2011/006967, filed on Dec. 14, 2011, which in turn claims thebenefit of Japanese Application No. 2010-286699, filed on Dec. 22, 2010,the disclosures of which Applications are incorporated by referenceherein.

BACKGROUND

1. Field

The present disclosure relates to zoom lens systems, interchangeablelens apparatuses, and camera systems.

2. Description of the Related Art

In recent years, interchangeable-lens type digital camera systems (alsoreferred to simply as “camera systems”, hereinafter) have been spreadingrapidly. Such interchangeable-lens type digital camera systems realize:taking of high-sensitive and high-quality images; high-speed focusingand high-speed image processing after image taking; and easy replacementof an interchangeable lens apparatus in accordance with a desired scene.Meanwhile, an interchangeable lens apparatus having a zoom lens systemthat forms an optical image with variable magnification is popularbecause it allows free change of focal length without the necessity oflens replacement.

Zoom lens systems having excellent optical performance from a wide-anglelimit to a telephoto limit have been desired as zoom lens systems to beused in interchangeable lens apparatuses. Various kinds of zoom lenssystems each having a negative lens unit located closest to an objectside, and a multiple-unit construction have been proposed.

Japanese Laid-Open Patent Publication No. 2005-092056 discloses a zoomlens having a four-unit construction of negative, positive, negative,and positive, wherein the interval between the first lens unit and thesecond lens unit decreases, the interval between the second lens unitand the third lens unit increases, and the interval between the thirdlens unit and the fourth lens unit decreases at a telephoto limit incomparison with at a wide-angle limit during zooming.

Japanese Laid-Open Patent Publication No. 2008-176271 discloses avariable magnification optical system having a four-unit construction ofnegative, positive, negative, and positive, wherein the interval betweenthe second lens unit and the third lens unit increases, and the intervalbetween the third lens unit and the fourth lens unit decreases duringmagnification change from a wide-angle limit to a telephoto limit, andwherein the whole of the third lens unit or a part of the third lensunit, as an image blur compensating lens unit, moves in a directionperpendicular to an optical axis.

SUMMARY

The present disclosure provides a compact and lightweight zoom lenssystem having short overall length of lens system and small outerdiameter of lens system, as well as in which various aberrations aresufficiently compensated and optical performance is excellent. Further,the present disclosure provides an interchangeable lens apparatus and acamera system each employing the zoom lens system.

The novel concepts disclosed herein were achieved in order to solve theforegoing problems in the related art, and herein is disclosed:

a zoom lens system, in order from an object side to an image side,comprising a first lens unit having negative optical power, a secondlens unit having positive optical power, a third lens unit havingnegative optical power, and a fourth lens unit having positive opticalpower, wherein

the second lens unit is, in order from the object side to the imageside, composed of an object-side second lens unit and an image-sidesecond lens unit,

the object-side second lens unit has positive optical power,

an aperture diaphragm is located between the object-side second lensunit and the image-side second lens unit, and

the following conditions (1) and (2) are satisfied:−0.5<f _(2O) /f _(2I)<1.0  (1)0.12<d _(2O) /f _(W)<0.35  (2)

where

f_(2O) is a composite focal length of the object-side second lens unit,

f_(2I) is a composite focal length of the image-side second lens unit,

d_(2O) is an optical axial distance from a most object side lens surfaceof the object-side second lens unit to the aperture diaphragm, and

f_(W) is a focal length of the entire system at a wide-angle limit.

The novel concepts disclosed herein were achieved in order to solve theforegoing problems in the related art, and herein is disclosed:

an interchangeable lens apparatus comprising:

a zoom lens system; and

a lens mount section which is connectable to a camera body including animage sensor for receiving an optical image formed by the zoom lenssystem and converting the optical image into an electric image signal,wherein

the zoom lens system, in order from an object side to an image side,comprises a first lens unit having negative optical power, a second lensunit having positive optical power, a third lens unit having negativeoptical power, and a fourth lens unit having positive optical power, inwhich

the second lens unit is, in order from the object side to the imageside, composed of an object-side second lens unit and an image-sidesecond lens unit,

the object-side second lens unit has positive optical power,

an aperture diaphragm is located between the object-side second lensunit and the image-side second lens unit, and

the following conditions (1) and (2) are satisfied:−0.5<f _(2O) /f _(2I)<1.0  (1)0.12<d _(2O) /f _(W)<0.35  (2)

where

f_(2O) is a composite focal length of the object-side second lens unit,

f_(2I) is a composite focal length of the image-side second lens unit,

d_(2O) is an optical axial distance from a most object side lens surfaceof the object-side second lens unit to the aperture diaphragm, and

f_(W) is a focal length of the entire system at a wide-angle limit.

The novel concepts disclosed herein were achieved in order to solve theforegoing problems in the related art, and herein is disclosed:

a camera system comprising:

an interchangeable lens apparatus including a zoom lens system; and

a camera body which is detachably connected to the interchangeable lensapparatus via a camera mount section, and includes an image sensor forreceiving an optical image formed by the zoom lens system and convertingthe optical image into an electric image signal, wherein

the zoom lens system, in order from an object side to an image side,comprises a first lens unit having negative optical power, a second lensunit having positive optical power, a third lens unit having negativeoptical power, and a fourth lens unit having positive optical power, inwhich

the second lens unit is, in order from the object side to the imageside, composed of an object-side second lens unit and an image-sidesecond lens unit,

the object-side second lens unit has positive optical power,

an aperture diaphragm is located between the object-side second lensunit and the image-side second lens unit, and

the following conditions (1) and (2) are satisfied:−0.5<f _(2O) /f _(2I)<1.0  (1)0.12<d _(2O) /f _(W)<0.35  (2)

where

f_(2O) is a composite focal length of the object-side second lens unit,

f_(2I) is a composite focal length of the image-side second lens unit,

d_(2O) is an optical axial distance from a most object side lens surfaceof the object-side second lens unit to the aperture diaphragm, and

f_(W) is a focal length of the entire system at a wide-angle limit.

The zoom lens system according to the present disclosure has shortoverall length of lens system and small outer diameter of lens system,as well as sufficiently compensated various aberrations and excellentoptical performance, and is compact and lightweight.

BRIEF DESCRIPTION OF THE DRAWINGS

This and other objects and features of the present disclosure willbecome clear from the following description, taken in conjunction withthe exemplary embodiments with reference to the accompanied drawings inwhich:

FIG. 1 is a lens arrangement diagram showing an infinity in-focuscondition of a zoom lens system according to Embodiment 1 (NumericalExample 1);

FIG. 2 is a longitudinal aberration diagram of an infinity in-focuscondition of a zoom lens system according to Numerical Example 1;

FIG. 3 is a longitudinal aberration diagram of a close-object in-focuscondition of a zoom lens system according to Numerical Example 1;

FIG. 4 is a lateral aberration diagram of a zoom lens system accordingto Numerical Example 1 at a telephoto limit in a basic state where imageblur compensation is not performed and in an image blur compensationstate;

FIG. 5 is a lens arrangement diagram showing an infinity in-focuscondition of a zoom lens system according to Embodiment 2 (NumericalExample 2);

FIG. 6 is a longitudinal aberration diagram of an infinity in-focuscondition of a zoom lens system according to Numerical Example 2;

FIG. 7 is a longitudinal aberration diagram of a close-object in-focuscondition of a zoom lens system according to Numerical Example 2;

FIG. 8 is a lens arrangement diagram showing an infinity in-focuscondition of a zoom lens system according to Embodiment 3 (NumericalExample 3);

FIG. 9 is a longitudinal aberration diagram of an infinity in-focuscondition of a zoom lens system according to Numerical Example 3;

FIG. 10 is a longitudinal aberration diagram of a close-object in-focuscondition of a zoom lens system according to Numerical Example 3;

FIG. 11 is a lateral aberration diagram of a zoom lens system accordingto Numerical Example 3 at a telephoto limit in a basic state where imageblur compensation is not performed and in an image blur compensationstate;

FIG. 12 is a lens arrangement diagram showing an infinity in-focuscondition of a zoom lens system according to Embodiment 4 (NumericalExample 4);

FIG. 13 is a longitudinal aberration diagram of an infinity in-focuscondition of a zoom lens system according to Numerical Example 4;

FIG. 14 is a longitudinal aberration diagram of a close-object in-focuscondition of a zoom lens system according to Numerical Example 4;

FIG. 15 is a lateral aberration diagram of a zoom lens system accordingto Numerical Example 4 at a telephoto limit in a basic state where imageblur compensation is not performed and in an image blur compensationstate; and

FIG. 16 is a schematic construction diagram of an interchangeable-lenstype digital camera system according to Embodiment 5.

DETAILED DESCRIPTION

Hereinafter, embodiments will be described with reference to thedrawings as appropriate. However, descriptions more detailed thannecessary may be omitted. For example, detailed description of alreadywell known matters or description of substantially identicalconfigurations may be omitted. This is intended to avoid redundancy inthe description below, and to facilitate understanding of those skilledin the art.

It should be noted that the applicants provide the attached drawings andthe following description so that those skilled in the art can fullyunderstand this disclosure. Therefore, the drawings and description arenot intended to limit the subject defined by the claims.

(Embodiments 1 to 4)

FIGS. 1, 5, 8, and 12 are lens arrangement diagrams of zoom lens systemsaccording to Embodiments 1 to 4, respectively, and each of the zoom lenssystems is in an infinity in-focus condition.

In each Fig., part (a) shows a lens configuration at a wide-angle limit(in the minimum focal length condition: focal length f_(w)), part (b)shows a lens configuration at a middle position (in an intermediatefocal length condition: focal length f_(M)=√(f_(w)*f_(T))), and part (c)shows a lens configuration at a telephoto limit (in the maximum focallength condition: focal length f_(T)). Further, in each Fig., each bentarrow located between part (a) and part (b) indicates a line obtained byconnecting the positions of each lens unit respectively at a wide-anglelimit, a middle position and a telephoto limit, in order from the top.In the part between the wide-angle limit and the middle position and thepart between the middle position and the telephoto limit, the positionsare connected simply with a straight line, and hence this line does notindicate actual motion of each lens unit.

Moreover, in each Fig., an arrow imparted to a lens unit indicatesfocusing from an infinity in-focus condition to a close-object in-focuscondition. That is, in FIGS. 1, 5, 8, and 12, the arrow indicates themoving direction of a third lens unit G3 described later, in focusingfrom an infinity in-focus condition to a close-object in-focuscondition. In FIGS. 1, 5, 8, and 12, since the symbols of the respectivelens units are imparted to part (a), the arrow indicating focusing isplaced beneath each symbol of each lens unit for the convenience sake.However, the direction along which each lens unit moves in focusing ineach zooming condition will be hereinafter described in detail for eachembodiment.

Each of the zoom lens systems according to Embodiments 1 to 4, in orderfrom the object side to the image side, comprises a first lens unit G1having negative optical power, a second lens unit G2 having positiveoptical power, a third lens unit G3 having negative optical power, and afourth lens unit G4 having positive optical power. In the zoom lenssystem according to each Embodiment, in zooming, the first lens unit G1,the second lens unit G2, and the third lens unit G3 individually move inthe direction along the optical axis so that the intervals between therespective lens units, i.e., the interval between the first lens unit G1and the second lens unit G2, the interval between the second lens unitG2 and the third lens unit G3, and the interval between the third lensunit G3 and the fourth lens unit G4, vary. In the zoom lens systemaccording to each Embodiment, these lens units are arranged in a desiredoptical power configuration, thereby achieving size reduction of theentire lens system while maintaining high optical performance.

In FIGS. 1, 5, 8, and 12, an asterisk “*” imparted to a particularsurface indicates that the surface is aspheric. In each Fig., symbol (+)or (−) imparted to the symbol of each lens unit corresponds to the signof the optical power of the lens unit. In each Fig., a straight linelocated on the most right-hand side indicates the position of an imagesurface S.

Further, as shown in FIG. 1, an aperture diaphragm A is located betweena third lens element L3 and a fourth lens element L4 in the second lensunit G2. As shown in FIGS. 5, 8, and 12, an aperture diaphragm A islocated between a fourth lens element L4 and a fifth lens element L5 inthe second lens unit G2. The location of each aperture diaphragm A willbe hereinafter described in detail for each embodiment.

(Embodiment 1)

As shown in FIG. 1, the first lens unit G1, in order from the objectside to the image side, comprises: a negative meniscus first lenselement L1 with the convex surface facing the object side; and apositive meniscus second lens element L2 with the convex surface facingthe object side. Each of the first lens element L1 and the second lenselement L2 has two aspheric surfaces.

The second lens unit G2, in order from the object side to the imageside, comprises: a bi-convex third lens element L3; a negative meniscusfourth lens element L4 with the convex surface facing the object side; abi-convex fifth lens element L5; a positive meniscus sixth lens elementL6 with the convex surface facing the image side; and a bi-concaveseventh lens element L7. Among these, the fourth lens element L4 and thefifth lens element L5 are cemented with each other, and the sixth lenselement L6 and the seventh lens element L7 are cemented with each other.The third lens element L3 has two aspheric surfaces, and the sixth lenselement L6 has an aspheric object side surface.

The third lens element L3 which is a component of the second lens unitG2 corresponds to an object-side second lens unit described later. Acemented lens element composed of the fourth lens element L4 and thefifth lens element L5, and a cemented lens element composed of the sixthlens element L6 and the seventh lens element L7, which are components ofthe second lens unit G2, correspond to an image-side second lens unitdescribed later. An aperture diaphragm A is located between the thirdlens element L3 and the fourth lens element L4, that is, between theobject-side second lens unit and the image-side second lens unit.

The third lens unit G3 comprises solely a negative meniscus eighth lenselement L8 with the convex surface facing the object side. The eighthlens element L8 has two aspheric surfaces.

The fourth lens unit G4 comprises solely a bi-convex ninth lens elementL9. The ninth lens element L9 has two aspheric surfaces.

The cemented lens element composed of the sixth lens element L6 and theseventh lens element L7, which are components of the second lens unitG2, corresponds to an image blur compensating lens unit described later,which moves in a direction perpendicular to the optical axis in order tooptically compensate image blur.

In zooming from a wide-angle limit to a telephoto limit at the time ofimage taking, the first lens unit G1 moves with locus of a convex to theimage side, the second lens unit G2 monotonically moves to the objectside, the third lens unit G3 monotonically and slightly moves to theobject side, and the fourth lens unit G4 is fixed with respect to theimage surface S. That is, in zooming, the first lens unit G1, the secondlens unit G2, and the third lens unit G3 individually move along theoptical axis such that the interval between the first lens unit G1 andthe second lens unit G2 decreases, the interval between the second lensunit G2 and the third lens unit G3 increases, and the interval betweenthe third lens unit G3 and the fourth lens unit G4 varies.

In focusing from an infinity in-focus condition to a close-objectin-focus condition, the third lens unit G3 moves to the image side alongthe optical axis in any zooming condition.

(Embodiment 2)

As shown in FIG. 5, the first lens unit G1, in order from the objectside to the image side, comprises: a negative meniscus first lenselement L1 with the convex surface facing the object side; a bi-concavesecond lens element L2; and a positive meniscus third lens element L3with the convex surface facing the object side. Among these, each of thefirst lens element L1 and the third lens element L3 has two asphericsurfaces.

The second lens unit G2, in order from the object side to the imageside, comprises: a bi-convex fourth lens element L4; a negative meniscusfifth lens element L5 with the convex surface facing the object side;and a bi-convex sixth lens element L6. Among these, the fifth lenselement L5 and the sixth lens element L6 are cemented with each other.The fourth lens element L4 has two aspheric surfaces.

The fourth lens element L4 which is a component of the second lens unitG2 corresponds to an object-side second lens unit described later. Acemented lens element composed of the fifth lens element L5 and thesixth lens element L6, which are components of the second lens unit G2,corresponds to an image-side second lens unit described later. Anaperture diaphragm A is located between the fourth lens element L4 andthe fifth lens element L5, that is, between the object-side second lensunit and the image-side second lens unit.

The third lens unit G3 comprises solely a bi-concave seventh lenselement L7. The seventh lens element L7 has two aspheric surfaces.

The fourth lens unit G4 comprises solely a bi-convex eighth lens elementL8. The eighth lens element L8 has an aspheric object side surface.

In zooming from a wide-angle limit to a telephoto limit at the time ofimage taking, the first lens unit G1 moves with locus of a convex to theimage side, the second lens unit G2 monotonically moves to the objectside, the third lens unit G3 monotonically and slightly moves to theobject side, and the fourth lens unit G4 is fixed with respect to theimage surface S. That is, in zooming, the first lens unit G1, the secondlens unit G2, and the third lens unit G3 individually move along theoptical axis such that the interval between the first lens unit G1 andthe second lens unit G2 decreases, the interval between the second lensunit G2 and the third lens unit G3 increases, and the interval betweenthe third lens unit G3 and the fourth lens unit G4 varies.

In focusing from an infinity in-focus condition to a close-objectin-focus condition, the third lens unit G3 moves to the image side alongthe optical axis in any zooming condition.

(Embodiment 3)

As shown in FIG. 8, the first lens unit G1, in order from the objectside to the image side, comprises: a negative meniscus first lenselement L1 with the convex surface facing the object side; a bi-concavesecond lens element L2; and a positive meniscus third lens element L3with the convex surface facing the object side. Among these, each of thefirst lens element L1 and the second lens element L2 has two asphericsurfaces.

The second lens unit G2, in order from the object side to the imageside, comprises: a positive meniscus fourth lens element L4 with theconvex surface facing the object side; a negative meniscus fifth lenselement L5 with the convex surface facing the object side; a bi-convexsixth lens element L6; and a bi-convex seventh lens element L7. Amongthese, the fifth lens element L5 and the sixth lens element L6 arecemented with each other. The fourth lens element L4 has two asphericsurfaces.

The fourth lens element L4 which is a component of the second lens unitG2 corresponds to an object-side second lens unit described later. Acemented lens element composed of the fifth lens element L5 and thesixth lens element L6, and the seventh lens element L7, which arecomponents of the second lens unit G2, correspond to an image-sidesecond lens unit described later. An aperture diaphragm A is locatedbetween the fourth lens element L4 and the fifth lens element L5, thatis, between the object-side second lens unit and the image-side secondlens unit.

The third lens unit G3 comprises solely a negative meniscus eighth lenselement L8 with the convex surface facing the object side. The eighthlens element L8 has two aspheric surfaces.

The fourth lens unit G4 comprises solely a bi-convex ninth lens elementL9. The ninth lens element L9 has two aspheric surfaces.

The seventh lens element L7 which is a component of the second lens unitG2 corresponds to an image blur compensating lens unit described later,which moves in a direction perpendicular to the optical axis in order tooptically compensate image blur.

In zooming from a wide-angle limit to a telephoto limit at the time ofimage taking, the first lens unit G1 moves with locus of a convex to theimage side, the second lens unit G2 monotonically moves to the objectside, the third lens unit G3 monotonically and slightly moves to theobject side, and the fourth lens unit G4 is fixed with respect to theimage surface S. That is, in zooming, the first lens unit G1, the secondlens unit G2, and the third lens unit G3 individually move along theoptical axis such that the interval between the first lens unit G1 andthe second lens unit G2 decreases, the interval between the second lensunit G2 and the third lens unit G3 increases, and the interval betweenthe third lens unit G3 and the fourth lens unit G4 varies.

In focusing from an infinity in-focus condition to a close-objectin-focus condition, the third lens unit G3 moves to the image side alongthe optical axis in any zooming condition.

(Embodiment 4)

As shown in FIG. 12, the first lens unit G1, in order from the objectside to the image side, comprises: a negative meniscus first lenselement L1 with the convex surface facing the object side; a negativemeniscus second lens element L2 with the convex surface facing the imageside; and a positive meniscus third lens element L3 with the convexsurface facing the object side. Among these, the second lens element L2has two aspheric surfaces.

The second lens unit G2, in order from the object side to the imageside, comprises: a bi-convex fourth lens element L4; a negative meniscusfifth lens element L5 with the convex surface facing the object side; abi-convex sixth lens element L6; and a bi-convex seventh lens elementL7. Among these, the fifth lens element L5 and the sixth lens element L6are cemented with each other. The fourth lens element L4 has twoaspheric surfaces.

The fourth lens element L4 which is a component of the second lens unitG2 corresponds to an object-side second lens unit described later. Acemented lens element composed of the fifth lens element L5 and thesixth lens element L6, and the seventh lens element L7, which arecomponents of the second lens unit G2, correspond to an image-sidesecond lens unit described later. An aperture diaphragm A is locatedbetween the fourth lens element L4 and the fifth lens element L5, thatis, between the object-side second lens unit and the image-side secondlens unit.

The third lens unit G3 comprises solely a bi-concave eighth lens elementL8. The eighth lens element L8 has two aspheric surfaces.

The fourth lens unit G4 comprises solely a bi-convex ninth lens elementL9. The ninth lens element L9 has two aspheric surfaces.

The seventh lens element L7 which is a component of the second lens unitG2 corresponds to an image blur compensating lens unit described later,which moves in a direction perpendicular to the optical axis in order tooptically compensate image blur.

In zooming from a wide-angle limit to a telephoto limit at the time ofimage taking, the first lens unit G1 moves with locus of a convex to theimage side, the second lens unit G2 monotonically moves to the objectside, the third lens unit G3 monotonically and slightly moves to theobject side, and the fourth lens unit G4 is fixed with respect to theimage surface S. That is, in zooming, the first lens unit G1, the secondlens unit G2, and the third lens unit G3 individually move along theoptical axis such that the interval between the first lens unit G1 andthe second lens unit G2 decreases, the interval between the second lensunit G2 and the third lens unit G3 increases, and the interval betweenthe third lens unit G3 and the fourth lens unit G4 varies.

In focusing from an infinity in-focus condition to a close-objectin-focus condition, the third lens unit G3 moves to the image side alongthe optical axis in any zooming condition.

The zoom lens systems according to Embodiments 1 to 4 each have afour-unit construction of negative, positive, negative, and positive, inwhich the second lens unit G2 is composed of two lens units of theobject-side second lens unit and the image-side second lens unit, andthe aperture diaphragm is located between the object-side second lensunit and the image-side second lens unit. Therefore, both of theinterval between the first lens unit G1 and the second lens unit G2, andthe interval between the second lens unit G2 and the third lens unit G3can be reduced, thereby realizing a reduction in the overall length oflens system.

In the zoom lens systems according to Embodiments 1 to 4, the third lensunit G3 moves along the optical axis in focusing from an infinityin-focus condition to a close-object in-focus condition, and lens unitseach having positive optical power, that is, the second lens unit G2 andthe fourth lens unit G4 are provided on each of the object side and theimage side of the third lens unit G3. Therefore, the negative opticalpower of the third lens unit G3 itself can be easily increased.Accordingly, the amount of movement of the third lens unit G3 can bereduced in focusing, and thus the overall length of lens system isreduced, and moreover, the overall length of lens system with the lensbarrel being retracted is also reduced.

In the zoom lens systems according to Embodiments 1 to 4, since thefourth lens unit G4 located closest to the image side is fixed withrespect to the image surface in zooming from a wide-angle limit to atelephoto limit at the time of image taking, entry of dust or the likeinto the lens system is sufficiently prevented. Further, since thenumber of cam components is reduced, the configuration of the lensbarrel can be simplified.

In the zoom lens systems according to Embodiments 1 to 4, since thefirst lens unit G1 located closest to the object side moves along theoptical axis in zooming from a wide-angle limit to a telephoto limit atthe time of image taking, the overall length of lens system is reduced,and moreover, the overall length of lens system with the lens barrelbeing retracted is also reduced.

The zoom lens systems according to Embodiments 1, 3, and 4 are eachprovided with an image blur compensating lens unit which moves in thedirection perpendicular to the optical axis. The image blur compensatinglens unit compensates image point movement caused by vibration of theentire system, that is, optically compensates image blur caused by handblurring, vibration and the like.

When compensating image point movement caused by vibration of the entiresystem, the image blur compensating lens unit moves in the directionperpendicular to the optical axis, so that image blur is compensated ina state that size increase in the entire zoom lens system is suppressedto realize a compact construction and that excellent imagingcharacteristics such as small decentering coma aberration and smalldecentering astigmatism are satisfied.

The image blur compensating lens unit according to the presentdisclosure may be a single lens unit. When a single lens unit iscomposed of a plurality of lens elements, the image blur compensatinglens unit may be any one lens element or a plurality of adjacent lenselements among the plurality of lens elements.

As described above, Embodiments 1 to 4 have been described as examplesof art disclosed in the present application. However, the art in thepresent disclosure is not limited to these embodiments. It is understoodthat various modifications, replacements, additions, omissions, and thelike have been performed in these embodiments to give optionalembodiments, and the art in the present disclosure can be applied to theoptional embodiments.

The following description is given for conditions that are beneficial tobe satisfied by a zoom lens system like the zoom lens systems accordingto Embodiments 1 to 4. Here, a plurality of beneficial conditions is setforth for the zoom lens system according to each embodiment. Aconstruction that satisfies all the plural conditions is most effectivefor the zoom lens system. However, when an individual condition issatisfied, a zoom lens system having the corresponding effect isobtained.

For example, in a zoom lens system like the zoom lens systems accordingto Embodiments 1 to 4, which comprises, in order from an object side toan image side, a first lens unit having negative optical power, a secondlens unit having positive optical power, a third lens unit havingnegative optical power, and a fourth lens unit having positive opticalpower, and in which the second lens unit is, in order from the objectside to the image side, composed of an object-side second lens unit andan image-side second lens unit, in which the object-side second lensunit has positive optical power, and in which an aperture diaphragm islocated between the object-side second lens unit and the image-sidesecond lens unit (this lens configuration is referred to as a basicconfiguration of the embodiments, hereinafter), the following conditions(1) and (2) are satisfied.−0.5<f _(2O) /f _(2I)<1.0  (1)0.12<d _(2O) /f _(W)<0.35  (2)

where

f_(2O) is a composite focal length of the object-side second lens unit,

f_(2I) is a composite focal length of the image-side second lens unit,

d_(2O) is an optical axial distance from a most object side lens surfaceof the object-side second lens unit to the aperture diaphragm, and

f_(W) is a focal length of the entire system at a wide-angle limit.

The condition (1) sets forth the relationship between the focal lengthof the object-side second lens unit and the focal length of theimage-side second lens unit. When the value goes below the lower limitof the condition (1), the negative optical power of the image-sidesecond lens unit becomes strong, and thereby the whole optical power ofthe second lens unit cannot be enhanced. When the value exceeds theupper limit of the condition (1), the optical power of the object-sidesecond lens unit becomes weak, and thereby a principal plane of thesecond lens unit is positioned nearer the image side thereof. As aresult, it becomes difficult to compensate aberrations at a telephotolimit.

When at least one of the following conditions (1)′ and (1)″ issatisfied, the above-mentioned effect is achieved more successfully.−0.3<f _(2O) /f _(2I)  (1)′f _(2O) /f _(2I)<0.7  (1)″

The condition (2) sets forth the relationship between the distance froma most object side lens surface of the object-side second lens unit tothe aperture diaphragm, and the focal length of the entire system at awide-angle limit. That is, the condition (2) relates to the location ofthe aperture diaphragm. When the value goes below the lower limit of thecondition (2), the diameter of the first lens unit becomes large, andthereby the outer diameter of lens system cannot be reduced. When thevalue exceeds the upper limit of the condition (2), upper light whichpasses through the upper part of each lens element at a wide-angle limitcannot be cut, and thereby it becomes difficult to compensateaberrations at a wide-angle limit.

When at least one of the following conditions (2)′ and (2)″ issatisfied, the above-mentioned effect is achieved more successfully.0.18<d _(2O) /f _(W)  (2)′d _(2O) /f _(W)<0.33  (2)″

It is beneficial that a zoom lens system having the basic configurationlike the zoom lens systems according to Embodiments 1 to 4 satisfies thefollowing condition (3).0.5<f _(2O) /f _(W)<3.0  (3)

where

f_(2O) is a composite focal length of the object-side second lens unit,and

f_(W) is a focal length of the entire system at a wide-angle limit.

The condition (3) sets forth the relationship between the focal lengthof the object-side second lens unit and the focal length of the entiresystem at a wide-angle limit. When the value goes below the lower limitof the condition (3), aberrations due to decentering of the object-sidesecond lens unit might become excessively large. When the value exceedsthe upper limit of the condition (3), a principal plane of theobject-side second lens unit is positioned nearer the image sidethereof, and thereby it becomes difficult to compensate aberrations at atelephoto limit.

When at least one of the following conditions (3)′ and (3)″ issatisfied, the above-mentioned effect is achieved more successfully.0.8<f _(2O) /f _(W)  (3)′f _(2O) /f _(W)<2.0  (3)″

It is beneficial that a zoom lens system having the basic configurationlike the zoom lens systems according to Embodiments 1 to 4 satisfies thefollowing condition (4).0.30<d ₁ /f _(W)<0.85  (4)

where

d₁ is an optical axial thickness of the first lens unit, and

f_(W) is a focal length of the entire system at a wide-angle limit.

The condition (4) sets forth the relationship between the thickness ofthe first lens unit and the focal length of the entire system at awide-angle limit. When the value goes below the lower limit of thecondition (4), the optical power of each lens element constituting thefirst lens unit cannot be increased, which might cause difficulty inreduction of the overall length of lens system. When the value exceedsthe upper limit of the condition (4), the overall length of lens systemincreases, which might cause increase also in the overall length of lenssystem with the lens barrel being retracted.

When at least one of the following conditions (4)′ and (4)″ issatisfied, the above-mentioned effect is achieved more successfully.0.4<d ₁ /f _(W)  (4)′d ₁ /f _(W)<0.7  (4)″

The individual lens units constituting the zoom lens systems accordingto Embodiments 1 to 4 are each composed exclusively of refractive typelens elements that deflect incident light by refraction (that is, lenselements of a type in which deflection is achieved at the interfacebetween media having different refractive indices). However, the presentinvention is not limited to this construction. For example, the lensunits may employ diffractive type lens elements that deflect incidentlight by diffraction; refractive-diffractive hybrid type lens elementsthat deflect incident light by a combination of diffraction andrefraction; or gradient index type lens elements that deflect incidentlight by distribution of refractive index in the medium. In particular,in the refractive-diffractive hybrid type lens element, when adiffraction structure is formed in the interface between media havingdifferent refractive indices, wavelength dependence of the diffractionefficiency is improved. Thus, such a configuration is beneficial.

(Embodiment 5)

FIG. 16 is a schematic construction diagram of an interchangeable-lenstype digital camera system according to Embodiment 5.

The interchangeable-lens type digital camera system 100 according toEmbodiment 5 includes a camera body 101, and an interchangeable lensapparatus 201 which is detachably connected to the camera body 101.

The camera body 101 includes: an image sensor 102 which receives anoptical image formed by a zoom lens system 202 of the interchangeablelens apparatus 201, and converts the optical image into an electricimage signal; a liquid crystal monitor 103 which displays the imagesignal obtained by the image sensor 102; and a camera mount section 104.On the other hand, the interchangeable lens apparatus 201 includes: azoom lens system 202 according to any of Embodiments 1 to 4; a lensbarrel 203 which holds the zoom lens system 202; and a lens mountsection 204 connected to the camera mount section 104 of the camera body101. The camera mount section 104 and the lens mount section 204 arephysically connected to each other. Moreover, the camera mount section104 and the lens mount section 204 function as interfaces which allowthe camera body 101 and the interchangeable lens apparatus 201 toexchange signals, by electrically connecting a controller (not shown) inthe camera body 101 and a controller (not shown) in the interchangeablelens apparatus 201. In FIG. 16, the zoom lens system according toEmbodiment 1 is employed as the zoom lens system 202.

In Embodiment 5, since the zoom lens system 202 according to any ofEmbodiments 1 to 4 is employed, a compact interchangeable lens apparatushaving excellent imaging performance can be realized at low cost.Moreover, size reduction and cost reduction of the entire camera system100 according to Embodiment 5 can be achieved. In the zoom lens systemsaccording to Embodiments 1 to 4, the entire zooming range need not beused. That is, in accordance with a desired zooming range, a range wheresatisfactory optical performance is obtained may exclusively be used.Then, the zoom lens system may be used as one having a lowermagnification than the zoom lens systems described in Embodiments 1 to4.

As described above, Embodiment 5 has been described as an example of artdisclosed in the present application. However, the art in the presentdisclosure is not limited to this embodiment. It is understood thatvarious modifications, replacements, additions, omissions, and the likehave been performed in this embodiment to give optional embodiments, andthe art in the present disclosure can be applied to the optionalembodiments.

Numerical examples are described below in which the zoom lens systemsaccording to Embodiments 1 to 4 are implemented. Here, in the numericalexamples, the units of length are all “mm”, while the units of viewangle are all “°”. Moreover, in the numerical examples, r is the radiusof curvature, d is the axial distance, nd is the refractive index to thed-line, and vd is the Abbe number to the d-line. In the numericalexamples, the surfaces marked with * are aspherical surfaces, and theaspherical surface configuration is defined by the following expression.

$Z = {\frac{h^{2}/r}{1 + \sqrt{1 - {\left( {1 + \kappa} \right)\left( {h/r} \right)^{2}}}} + {\sum\;{A_{n}h^{n}}}}$Here, the symbols in the formula indicate the following quantities.

Z is a distance from a point on an aspherical surface at a height hrelative to the optical axis to a tangential plane at the vertex of theaspherical surface,

h is a height relative to the optical axis,

r is a radius of curvature at the top,

κ is a conic constant, and

An is a n-th order aspherical coefficient.

FIGS. 2, 6, 9, and 13 are longitudinal aberration diagrams of aninfinity in-focus condition of the zoom lens systems according toNumerical Examples 1 to 4, respectively.

FIGS. 3, 7, 10, and 14 are longitudinal aberration diagrams of aclose-object in-focus condition of the zoom lens systems according toNumerical Examples 1 to 4, respectively. The object distance in each ofNumerical Examples 1 to 4 is 300 mm.

In each longitudinal aberration diagram, part (a) shows the aberrationat a wide-angle limit, part (b) shows the aberration at a middleposition, and part (c) shows the aberration at a telephoto limit. Eachlongitudinal aberration diagram, in order from the left-hand side, showsthe spherical aberration (SA (mm)), the astigmatism (AST (mm)) and thedistortion (DIS (%)). In each spherical aberration diagram, the verticalaxis indicates the F-number (in each Fig., indicated as F), and thesolid line, the short dash line and the long dash line indicate thecharacteristics to the d-line, the F-line and the C-line, respectively.In each astigmatism diagram, the vertical axis indicates the imageheight (in each Fig., indicated as H), and the solid line and the dashline indicate the characteristics to the sagittal plane (in each Fig.,indicated as “s”) and the meridional plane (in each Fig., indicated as“m”), respectively. In each distortion diagram, the vertical axisindicates the image height (in each Fig., indicated as H).

FIGS. 4, 11, and 15 are lateral aberration diagrams of the zoom lenssystems at a telephoto limit according to Numerical Examples 1, 3, and4, respectively.

In each lateral aberration diagram, the aberration diagrams in the upperthree parts correspond to a basic state where image blur compensation isnot performed at a telephoto limit, while the aberration diagrams in thelower three parts correspond to an image blur compensation state wherethe image blur compensating lens unit (Numerical Example 1: the cementedlens element composed of the sixth lens element L6 and the seventh lenselement L7, Numerical Examples 3 and 4: the seventh lens element L7) ismoved by a predetermined amount in a direction perpendicular to theoptical axis at a telephoto limit. Among the lateral aberration diagramsof a basic state, the upper part shows the lateral aberration at animage point of 70% of the maximum image height, the middle part showsthe lateral aberration at the axial image point, and the lower partshows the lateral aberration at an image point of −70% of the maximumimage height. Among the lateral aberration diagrams of an image blurcompensation state, the upper part shows the lateral aberration at animage point of 70% of the maximum image height, the middle part showsthe lateral aberration at the axial image point, and the lower partshows the lateral aberration at an image point of −70% of the maximumimage height. In each lateral aberration diagram, the horizontal axisindicates the distance from the principal ray on the pupil surface, andthe solid line, the short dash line and the long dash line indicate thecharacteristics to the d-line, the F-line and the C-line, respectively.In each lateral aberration diagram, the meridional plane is adopted asthe plane containing the optical axis of the first lens unit G1 and theoptical axis of the second lens unit G2.

In the zoom lens system according to each Numerical Example, the amountof movement of the image blur compensating lens unit in a directionperpendicular to the optical axis in an image blur compensation state ata telephoto limit is as follows.

Numerical Example Amount of movement (mm) 1 0.457 3 0.182 4 0.316

When the shooting distance is infinity, at a telephoto limit, the amountof image decentering in a case that the zoom lens system inclines by0.3° is equal to the amount of image decentering in a case that theimage blur compensating lens unit displaces in parallel by each of theabove-mentioned values in a direction perpendicular to the optical axis.

As seen from the lateral aberration diagrams, satisfactory symmetry isobtained in the lateral aberration at the axial image point. Further,when the lateral aberration at the +70% image point and the lateralaberration at the −70% image point are compared with each other in thebasic state, all have a small degree of curvature and almost the sameinclination in the aberration curve. Thus, decentering coma aberrationand decentering astigmatism are small. This indicates that sufficientimaging performance is obtained even in the image blur compensationstate. Further, when the image blur compensation angle of a zoom lenssystem is the same, the amount of parallel translation required forimage blur compensation decreases with decreasing focal length of theentire zoom lens system. Thus, at arbitrary zoom positions, sufficientimage blur compensation can be performed for image blur compensationangles up to 0.3° without degrading the imaging characteristics.

NUMERICAL EXAMPLE 1

The zoom lens system of Numerical Example 1 corresponds to Embodiment 1shown in FIG. 1. Table 1 shows the surface data of the zoom lens systemof Numerical Example 1. Table 2 shows the aspherical data. Table 3 showsvarious data in an infinity in-focus condition. Table 4 shows variousdata in a close-object in-focus condition.

TABLE 1 (Surface data) Surface number r d nd vd Object surface ∞  1*7246.07820 0.80000 1.77200 50.0  2* 9.76630 3.77470  3* 15.61040 1.751302.00170 20.6  4* 23.59990 Variable  5* 10.99500 2.32880 1.69385 53.1  6*−46.84230 1.39640  7 (Diaphragm) ∞ 2.00000  8 81.47730 0.40000 1.8502632.3  9 6.78960 2.72250 1.49700 81.6 10 −14.43410 0.50000 11* −52.863501.18010 1.81000 41.0 12 −21.55830 0.30000 1.48749 70.4 13 46.44870Variable 14* 1000.00000 0.60000 1.77200 50.0 15* 15.45450 Variable 16*38.47910 3.71710 1.85400 40.4 17* −48.71800 (BF) Image surface ∞

TABLE 2 (Aspherical data) Surface No. 1 K = 0.00000E+00, A4 =1.06900E−04, A6 = −1.23164E−06, A8 = 3.36463E−09 A10 = 8.54528E−13Surface No. 2 K = 0.00000E+00, A4 = −5.29613E−05, A6 = 1.38564E−06, A8 =−2.42278E−08 A10 = −9.75451E−11 Surface No. 3 K = 0.00000E+00, A4 =−2.71820E−04, A6 = 1.40876E−06, A8 = 0.00000E+00 A10 = 0.00000E+00Surface No. 4 K = 0.00000E+00, A4 = −2.56009E−04, A6 = 1.00320E−06, A8 =0.00000E+00 A10 = 0.00000E+00 Surface No. 5 K = 0.00000E+00, A4 =−6.09544E−05, A6 = −5.78175E−08, A8 = 0.00000E+00 A10 = 0.00000E+00Surface No. 6 K = 0.00000E+00, A4 = 7.98019E−05, A6 = −3.37082E−07, A8 =1.48113E−08 A10 = −2.44475E−10 Surface No. 11 K = 0.00000E+00, A4 =−1.28683E−05, A6 = −7.75752E−07, A8 = 1.15009E−07 A10 = −3.34531E−09Surface No. 14 K = 0.00000E+00, A4 = −1.94531E−04, A6 = 2.03325E−08, A8= 0.00000E+00 A10 = 0.00000E+00 Surface No. 15 K = 0.00000E+00, A4 =−1.89186E−04, A6 = 6.83816E−08, A8 = 0.00000E+00 A10 = 0.00000E+00Surface No. 16 K = 0.00000E+00, A4 = −2.43333E−05, A6 = 2.10209E−07, A8= −1.20236E−09 A10 = 3.61521E−12 Surface No. 17 K = 0.00000E+00, A4 =−3.55533E−05, A6 = 1.46031E−07, A8 = 0.00000E+00 A10 = 0.00000E+00

TABLE 3 (Various data in an infinity in-focus condition) Zooming ratio2.79710 Wide-angle Middle Telephoto limit position limit Focal length14.4901 24.2340 40.5304 F-number 3.64054 5.30513 5.82425 View angle40.5973 24.2052 14.7083 Image height 10.8150 10.8150 10.8150 Overalllength 60.5693 55.6705 60.5698 of lens system BF 14.1990 14.1990 14.1990d4 17.8853 6.8869 0.6000 d13 1.9392 8.0113 17.2462 d15 5.0745 5.10187.0529 Zoom lens unit data Lens Initial Focal unit surface No. length 11 −19.77079 2 5 15.73323 3 14 −20.33850 4 16 25.67835

TABLE 4 (Various data in a close-object in-focus condition) Wide-angleMiddle Telephoto limit position limit Object distance 300.0000 300.0000300.0000 BF 14.1990 14.1990 14.1990 d4 17.8853 6.8869 0.6000 d13 2.41009.3719 21.0126 d15 4.6037 3.7412 3.2864

NUMERICAL EXAMPLE 2

The zoom lens system of Numerical Example 2 corresponds to Embodiment 2shown in FIG. 5. Table 5 shows the surface data of the zoom lens systemof Numerical Example 2. Table 6 shows the aspherical data. Table 7 showsvarious data in an infinity in-focus condition. Table 8 shows variousdata in a close-object in-focus condition.

TABLE 5 (Surface data) Surface number r d nd vd Object surface ∞  1*24.26410 0.90000 1.81000 41.0  2* 10.38930 5.28250  3 −26.13930 0.600001.61800 63.4  4 55.82340 0.20000  5* 12.45890 1.36570 2.01960 21.5  6*17.93070 Variable  7* 11.91240 3.08090 1.77200 50.0  8* −72.977301.50000  9 (Diaphragm) ∞ 1.50000 10 578.36700 0.30000 1.80610 33.3 117.32500 2.64380 1.49700 81.6 12 −14.76640 Variable 13* −93.84910 0.500001.54000 56.0 14* 13.12940 Variable 15* 40.68890 3.06480 1.85400 40.4 16−64.48970 (BF) Image surface ∞

TABLE 6 (Aspherical data) Surface No. 1 K = 0.00000E+00, A4 =7.20660E−05, A6 = −1.76669E−07, A8 = 0.00000E+00 A10 = 0.00000E+00Surface No. 2 K = 0.00000E+00, A4 = 2.37301E−05, A6 = 4.41999E−07, A8 =0.00000E+00 A10 = 0.00000E+00 Surface No. 5 K = 0.00000E+00, A4 =−1.43956E−04, A6 = 1.78509E−06, A8 = 0.00000E+00 A10 = 0.00000E+00Surface No. 6 K = 0.00000E+00, A4 = −7.82448E−05, A6 = 1.98131E−06, A8 =0.00000E+00 A10 = 0.00000E+00 Surface No. 7 K = 0.00000E+00, A4 =−2.77853E−05, A6 = 3.01868E−07, A8 = 0.00000E+00 A10 = 0.00000E+00Surface No. 8 K = 0.00000E+00, A4 = 9.37123E−05, A6 = −1.02967E−07, A8 =8.87091E−09 A10 = −6.74560E−11 Surface No. 13 K = 0.00000E+00, A4 =−1.64682E−04, A6 = 6.28293E−07, A8 = 0.00000E+00 A10 = 0.00000E+00Surface No. 14 K = 0.00000E+00, A4 = −1.42056E−04, A6 = −1.38794E−07, A8= 0.00000E+00 A10 = 0.00000E+00 Surface No. 15 K = 0.00000E+00, A4 =1.88815E−05, A6 = −5.91514E−08, A8 = 0.00000E+00 A10 = 0.00000E+00

TABLE 7 (Various data in an infinity in-focus condition) Zooming ratio2.79710 Wide-angle Middle Telephoto limit position limit Focal length14.4901 24.2340 40.5302 F-number 3.64081 5.30486 5.82421 View angle41.1705 24.3636 14.8033 Image height 10.8150 10.8150 10.8150 Overalllength 61.5691 56.8414 61.2610 of lens system BF 14.1990 14.1990 14.1990d6 17.1452 6.6315 0.6000 d12 3.1505 8.9183 17.7188 d14 6.1365 6.15477.8054 Zoom lens unit data Lens Initial Focal unit surface No. length 11 −18.64438 2 7 14.98819 3 13 −21.29480 4 15 29.61077

TABLE 8 (Various data in a close-object in-focus condition) Wide-angleMiddle Telephoto limit position limit Object distance 300.0000 300.0000300.0000 BF 14.1990 14.1990 14.1990 d6 17.1452 6.6315 0.6000 d12 3.576610.1476 21.1244 d14 5.7104 4.9254 4.3998

NUMERICAL EXAMPLE 3

The zoom lens system of Numerical Example 3 corresponds to Embodiment 3shown in FIG. 8. Table 9 shows the surface data of the zoom lens systemof Numerical Example 3. Table 10 shows the aspherical data. Table 11shows various data in an infinity in-focus condition. Table 12 showsvarious data in a close-object in-focus condition.

TABLE 9 (Surface data) Surface number r d nd vd Object surface ∞  1*15.78210 0.80000 1.85400 40.4  2* 9.12530 5.45050  3* −16.56950 0.600001.58700 59.6  4* 77.97690 0.20000  5 18.36590 1.17940 2.00272 19.3  628.11850 Variable  7* 11.62750 1.87230 1.75550 45.6  8* 106.418401.11400  9 (Diaphragm) ∞ 2.00000 10 20.59090 0.40000 1.90366 31.3 117.48610 2.92480 1.49700 81.6 12 −28.73240 0.50000 13 29.59400 1.300001.56732 42.8 14 −122.15880 Variable 15* 38.37840 0.40000 1.81000 41.016* 9.04180 Variable 17* 63.45900 3.58470 1.75550 45.6 18* −36.13590(BF) Image surface ∞

TABLE 10 (Aspherical data) Surface No. 1 K = 0.00000E+00, A4 =0.00000E+00, A6 = 5.99515E−07, A8 = 0.00000E+00 A10 = 0.00000E+00Surface No. 2 K = 0.00000E+00, A4 = −2.47760E−05, A6 = −1.49379E−08, A8= 9.35895E−09 A10 = 1.19674E−11 Surface No. 3 K = 0.00000E+00, A4 =−1.55227E−05, A6 = 4.44467E−07, A8 = 1.62023E−08 A10 = −1.66412E−10Surface No. 4 K = 0.00000E+00, A4 = 0.00000E+00, A6 = 1.14114E−06, A8 =0.00000E+00 A10 = 0.00000E+00 Surface No. 7 K = 0.00000E+00, A4 =−3.55890E−05, A6 = −5.87816E−07, A8 = 2.39229E−08 A10 = −2.31393E−09Surface No. 8 K = 0.00000E+00, A4 = 5.59122E−05, A6 = −8.26971E−07, A8 =1.66233E−08 A10 = −2.32755E−09 Surface No. 15 K = 0.00000E+00, A4 =−2.83318E−04, A6 = 2.24454E−07, A8 = −1.44655E−08 A10 = 7.84135E−10Surface No. 16 K = 0.00000E+00, A4 = −2.71306E−04, A6 = −2.85318E−06, A8= 0.00000E+00 A10 = 0.00000E+00 Surface No. 17 K = 0.00000E+00, A4 =4.73183E−05, A6 = −1.18300E−07, A8 = 0.00000E+00 A10 = 0.00000E+00Surface No. 18 K = 0.00000E+00, A4 = −9.29919E−06, A6 = 4.89106E−08, A8= 0.00000E+00 A10 = 0.00000E+00

TABLE 11 (Various data in an infinity in-focus condition) Zooming ratio2.79707 Wide-angle Middle Telephoto limit position limit Focal length14.4901 24.2339 40.5297 F-number 3.64044 5.30477 5.82432 View angle40.6348 24.5553 14.9715 Image height 10.8150 10.8150 10.8150 Overalllength 61.5690 57.7455 60.3986 of lens system BF 14.1990 14.1990 14.1990d6 15.9237 6.4273 0.6000 d14 3.2316 7.4620 14.3893 d16 5.8888 7.33148.8853 Zoom lens unit data Lens Initial Focal unit surface No. length 11 −15.29116 2 7 13.08509 3 15 −14.69287 4 17 30.95568

TABLE 12 (Various data in a close-object in-focus condition) Wide-angleMiddle Telephoto limit position limit Object distance 300.0000 300.0000300.0000 BF 14.1990 14.1990 14.1990 d6 15.9237 6.4273 0.6000 d14 3.46448.0869 16.0861 d16 5.6560 6.7064 7.1885

NUMERICAL EXAMPLE 4

The zoom lens system of Numerical Example 4 corresponds to Embodiment 4shown in FIG. 12. Table 13 shows the surface data of the zoom lenssystem of Numerical Example 4. Table 14 shows the aspherical data. Table15 shows various data in an infinity in-focus condition. Table 16 showsvarious data in a close-object in-focus condition.

TABLE 13 (Surface data) Surface number r d nd vd Object surface ∞  120.78970 0.75000 1.91082 35.2  2 9.66470 5.38180  3* −20.85130 0.450001.58700 59.6  4* −1000.00000 0.20000  5 31.05800 1.39550 1.94595 18.0  6110.64730 Variable  7* 12.23870 2.08550 1.77200 50.0  8* −173.853301.00000  9 (Diaphragm) ∞ 2.17440 10 42.56150 0.91310 1.80610 33.3 117.04990 2.63610 1.49700 81.6 12 −27.37000 1.50000 13 43.19420 1.255801.53172 48.8 14 −206.12520 Variable 15* −175.97430 0.30000 1.81000 41.016* 13.23860 Variable 17* 46.66870 3.36070 1.81000 41.0 18* −48.04510(BF) Image surface ∞

TABLE 14 (Aspherical data) Surface No. 3 K = 0.00000E+00, A4 =7.69222E−05, A6 = −3.15767E−06, A8 = 3.88535E−08 A10 = −2.93421E−10Surface No. 4 K = 0.00000E+00, A4 = 3.22844E−05, A6 = −3.16521E−06, A8 =3.65830E−08 A10 = −2.45708E−10 Surface No. 7 K = 0.00000E+00, A4 =−3.89924E−05, A6 = 1.23500E−06, A8 = −5.24843E−08 A10 = 7.15332E−10Surface No. 8 K = 0.00000E+00, A4 = 4.14186E−05, A6 = 1.03201E−06, A8 =−5.09447E−08 A10 = 7.48549E−10 Surface No. 15 K = 0.00000E+00, A4 =1.00000E−04, A6 = −6.51647E−06, A8 = 1.03955E−07 A10 = 3.85551E−10Surface No. 16 K = 0.00000E+00, A4 = 1.23214E−04, A6 = −6.41298E−06, A8= 7.58562E−08 A10 = 3.50682E−10 Surface No. 17 K = 0.00000E+00, A4 =−2.33445E−05, A6 = 4.80516E−07, A8 = −1.02686E−09 A10 = −3.03671E−11Surface No. 18 K = 0.00000E+00, A4 = −3.49005E−05, A6 = 1.41732E−07, A8= 4.37798E−09 A10 = −5.44451E−11

TABLE 15 (Various data in an infinity in-focus condition) Zooming ratio2.79710 Wide-angle Middle Telephoto limit position limit Focal length14.4901 24.2340 40.5302 F-number 3.64019 5.61748 5.82496 View angle40.0390 24.2623 14.6961 Image height 10.8150 10.8150 10.8150 Overalllength 65.5690 59.1630 60.3466 of lens system BF 14.1990 14.1990 14.1990d6 19.8761 7.8944 0.6000 d14 2.0672 6.2175 12.9350 d16 6.0236 7.44909.2094 Zoom lens unit data Lens Initial Focal unit surface No. length 11 −18.10745 2 7 14.50829 3 15 −15.18970 4 17 29.69817

TABLE 16 (Various data in a close-object in-focus condition) Wide-angleMiddle Telephoto limit position limit Object distance 300.0000 300.0000300.0000 BF 14.1990 14.1990 14.1990 d6 19.8761 7.8944 0.6000 d14 2.32006.9003 14.7863 d16 5.7708 6.7662 7.3581

The following Table 17 shows the corresponding values to the individualconditions in the zoom lens systems of each of Numerical Examples.

TABLE 17 (Values corresponding to conditions) Numerical ExampleCondition 1 2 3 4 (1) f_(2O)/f_(2I) −0.21 −0.06 0.54 0.15 (2)d_(2O)/f_(W) 0.26 0.32 0.21 0.21 (3) f_(2O)/f_(W) 0.90 0.93 1.18 1.03(4) d₁/f_(W) 0.44 0.58 0.57 0.56

The present disclosure is applicable to a digital still camera, adigital video camera, a camera for a mobile terminal device such as asmart-phone, a camera for a PDA (Personal Digital Assistance), asurveillance camera in a surveillance system, a Web camera, avehicle-mounted camera or the like. In particular, the presentdisclosure is applicable to a photographing optical system where highimage quality is required like in a digital still camera system or adigital video camera system.

Also, the present disclosure is applicable to, among the interchangeablelens apparatuses according to the present disclosure, an interchangeablelens apparatus having motorized zoom function, i.e., activating functionfor the zoom lens system by a motor, with which a digital video camerasystem is provided.

As described above, embodiments have been described as examples of artin the present disclosure. Thus, the attached drawings and detaileddescription have been provided.

Therefore, in order to illustrate the art, not only essential elementsfor solving the problems but also elements that are not necessary forsolving the problems may be included in elements appearing in theattached drawings or in the detailed description. Therefore, suchunnecessary elements should not be immediately determined as necessaryelements because of their presence in the attached drawings or in thedetailed description.

Further, since the embodiments described above are merely examples ofthe art in the present disclosure, it is understood that variousmodifications, replacements, additions, omissions, and the like can beperformed in the scope of the claims or in an equivalent scope thereof.

What is claimed is:
 1. A zoom lens system, in order from an object sideto an image side, comprising a first lens unit having negative opticalpower, a second lens unit having positive optical power, a third lensunit having negative optical power, and a fourth lens unit havingpositive optical power, wherein the second lens unit is, in order fromthe object side to the image side, composed of an object-side secondlens unit and an image-side second lens unit, the object-side secondlens unit has positive optical power, an aperture diaphragm is locatedbetween the object-side second lens unit and the image-side second lensunit, and the following conditions (1) and (2) are satisfied:−0.5<f _(2O) /f _(2I)<1.0  (1)0.12<d _(2O) /f _(W)<0.35  (2) where f_(2O) is a composite focal lengthof the object-side second lens unit, f_(2I) is a composite focal lengthof the image-side second lens unit, d_(2O) is an optical axial distancefrom a most object side lens surface of the object-side second lens unitto the aperture diaphragm, and f_(W) is a focal length of the entiresystem at a wide-angle limit.
 2. The zoom lens system as claimed inclaim 1, wherein the following condition (3) is satisfied:0.5<f _(2O) /f _(W)<3.0  (3) where f_(2O) is a composite focal length ofthe object-side second lens unit, and f_(W) is a focal length of theentire system at a wide-angle limit.
 3. The zoom lens system as claimedin claim 1, wherein the third lens unit moves along an optical axis, infocusing from an infinity in-focus condition to a close-object in-focuscondition.
 4. The zoom lens system as claimed in claim 1, wherein thefollowing condition (4) is satisfied:0.30<d ₁ /f _(W)<0.85  (4) where d₁ is an optical axial thickness of thefirst lens unit, and f_(W) is a focal length of the entire system at awide-angle limit.
 5. The zoom lens system as claimed in claim 1, whereinthe fourth lens unit is fixed with respect to an image surface, inzooming from a wide-angle limit to a telephoto limit at the time ofimage taking.
 6. The zoom lens system as claimed in claim 1, wherein thefirst lens unit moves along an optical axis, in zooming from awide-angle limit to a telephoto limit at the time of image taking.
 7. Aninterchangeable lens apparatus comprising: the zoom lens system asclaimed in claim 1; and a lens mount section which is connectable to acamera body including an image sensor for receiving an optical imageformed by the zoom lens system and converting the optical image into anelectric image signal.
 8. A camera system comprising: an interchangeablelens apparatus including the zoom lens system as claimed in claim 1; anda camera body which is detachably connected to the interchangeable lensapparatus via a camera mount section, and includes an image sensor forreceiving an optical image formed by the zoom lens system and convertingthe optical image into an electric image signal.